JP2016055352A - Abrasive slurry - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abrasive slurry which does not cause aggregation in the long term storage of abrasive particles, is excellent in dispersion stability and scratch resistance at polishing and having high abrasive speed.SOLUTION: An abrasive slurry includes the core-shell type abrasive particles in which the core and shell have compositions different from each other. The core of the core-shell type abrasive particles includes as a main component, the oxide of at least one metal element selected from the group of specific metal elements, and the shell includes cerium oxide as a main component and the oxide of at least one metal element selected from the group of specific metal elements as an accessory component. The core and shell include at least one of oxides (including cerium oxide) of the same metal element as each other. Besides, the variation coefficient of a particle size distribution in the core-shell type abrasive particles is 20% or less, and the average value of the zeta potential of the above core-shell type abrasive particles is within the range of -120 to -30 mV.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an abrasive slurry containing core-shell type abrasive particles having a specific multilayer structure.

  As an abrasive that precisely polishes optical glass and semiconductor devices in the finishing process, a rare earth element oxide, which is mainly composed of cerium oxide and lanthanum oxide, neodymium oxide, praseodymium oxide, etc., has been used. . Other abrasives include diamond, iron oxide, aluminum oxide, zirconium oxide, colloidal silica, etc., but when compared in terms of polishing rate and surface roughness of the polished object, cerium oxide Is known to be effective and is now widely used.

  However, cerium oxide itself is unevenly distributed worldwide, and it is difficult to say that supply is stabilized. For such problems, development of an abrasive that can polish glass with high accuracy while reducing the amount of cerium oxide used is eagerly desired.

  As a method for producing a high-purity cerium oxide-based abrasive that can be precisely polished in a finishing process such as optical glass, a purified aqueous solution of cerium nitrate, cerous chloride, cerous sulfate, etc. Add salts of carbonic acid, oxalic acid, acetic acid, etc. to precipitate products such as cerium carbonate, cerous oxalate, cerous acetate, filter this precipitate, dry it, and fire it. There is a method for obtaining cerium oxide.

  For example, Patent Document 1 describes a method for obtaining a cerium-based abrasive having a crystallite diameter of 20 to 40 nm obtained by firing at a temperature of 850 to 1100 ° C. for 1 to 10 hours. In this method, a cerium-based abrasive is produced by mixing and grinding a mixed rare earth oxide and a mixed rare earth fluoride. However, since the cerium-based abrasive obtained by the method disclosed in Patent Document 1 has a low cerium concentration on the outermost surface of the particles, the polishing ability is low and a sufficient polishing rate cannot be obtained.

  In particular, in recent years, glass substrates for hard disks are listed as objects to be polished, but glass substrates for hard disks have mechanical properties, in particular, hardness and hardness, in order to suppress disk shake when rotating at high speed. The demand for improved rigidity is increasing year by year. In order to satisfy these mechanical property requirements, a tempered glass substrate mainly composed of aminosilicate and a crystallized glass substrate mainly composed of lithium silicate have been used.

  These glass substrates have excellent chemical resistance and are hard and thus have poor workability. With the cerium-based abrasive obtained by the method disclosed in Patent Document 1, the polishing rate becomes extremely slow. End up. Moreover, since these glass substrates are harder than the conventional glass substrate, there exists a problem that a board | substrate is easily damaged by applying a high pressure compared with the case where the conventional glass substrate is grind | polished.

  On the other hand, Non-Patent Document 1 proposes a method of obtaining particles by heating and stirring a cerium (III) nitrate aqueous solution, an yttrium nitrate (III) aqueous solution, and an aqueous solution mixed with urea.

  Patent Document 2 discloses that a core formed of base particles made of an inorganic material having a specific gravity smaller than that of cerium oxide and fine particles containing cerium oxide having a particle size smaller than that of the base particles are bonded to the outside of the base particles. An abrasive containing composite abrasive grains having a shell formed by being bonded together is described.

  This abrasive is added to a dispersion in which silicon oxide particles as base particles are dispersed while stirring, and further added to a dispersion in which cerium oxide particles are dispersed while stirring. The obtained solid particles (silicon oxide) and fine particles (cerium oxide) were bonded to each other via a binder (aluminum oxide), and the solid was separated into solid and liquid, and the separated solid was baked at 700 to 900 ° C. It is described that it can be obtained by pulverizing a fired product with a dry jet mill.

  In this method, by adopting a core / shell structure having a base particle (core) made of silicon oxide and a shell containing cerium oxide formed by being bonded to the outside of the base particle by a binder in this method, It is said that while reducing the amount of cerium oxide used, it is possible to obtain the same polishing accuracy and polishing rate as conventional products.

  However, as a result of firing the particles produced by the method of Non-Patent Document 1 and confirming the effect as an abrasive, the polishing rate was low. This is considered to be because a large amount of elements other than cerium (yttrium) are mixed on the particle surface in order to adjust the particle shape and particle size distribution.

  In addition, the abrasive particles containing particles produced by the method of Non-Patent Document 1 and cerium oxide bonded by the binder obtained by the method of Patent Document 2 have a wide particle size distribution, and the abrasive slurry is used over a long period of time. In the process, or in the long-term storage process of the abrasive slurry, the abrasive particles are likely to agglomerate.As a result, in the polishing process, the generated agglomerates and the like may cause scratches on the glass substrate, and the surface smoothness may be impaired. Alternatively, the tempered glass substrate mainly composed of aminosilicate as described above and the crystallized glass substrate mainly composed of lithium silicate have a problem that the polishing rate is lowered.

Japanese Patent No. 3949147 JP2012-11525A

J. et al. Am. Ceram. Soc. 71, No. 10, 845-853 (1988)

  The object of the present invention has been made in view of the above problems and situations, and the solution is to achieve excellent dispersion stability without scratching the abrasive particles during storage over a long period of time, and scratch resistance during polishing. It is an object to provide an abrasive slurry that is excellent in resistance and has a high polishing rate.

  As a result of intensive studies in view of the above problems, the present inventor has a core and a shell having different compositions, the core is mainly composed of an oxide of a specific metal element, and the shell is composed of cerium oxide as the main component. And core-shell type abrasive particles that contain an oxide of a specific metal element as an accessory component, have high monodispersibility, and have an average value of zeta potential in the range of −120 to −30 mV. With the abrasive slurry characterized by the above, it is possible to realize an abrasive slurry that has excellent dispersion stability, excellent scratch resistance during polishing, and high polishing speed without causing aggregation of core-shell type abrasive particles. It is as soon as it has been found and can be achieved.

  That is, the said subject which concerns on this invention is solved by the following means.

1. An abrasive slurry containing core-shell type abrasive particles each having a core and a shell having different compositions,
The core of the core / shell type abrasive particle contains an oxide of at least one metal element selected from the following metal element group as a main component, and the shell contains cerium oxide as a main component and the following metal as a sub component. Containing at least one metal element oxide selected from the element group,
The core and shell contain at least one oxide of the same metal element (including cerium oxide), and the coefficient of variation in the particle size distribution of the core-shell type abrasive particles represented by the following formula (1) 20% or less,
And the average value of the zeta potential of the core-shell type abrasive particles is in the range of -120 to -30 mV.

Metal element group: Ti (titanium), Sr (strontium), Y (yttrium), Ba (barium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium)
Formula (1)
Coefficient of variation of particle size distribution of core / shell type abrasive particles (%) = (standard deviation of particle size distribution of core / shell type abrasive particles / average particle size of core / shell type abrasive particles) × 100
2. 2. The abrasive slurry according to item 1, wherein the pH of the abrasive slurry in terms of 25 ° C. is adjusted within a range of 3.0 to 11.0 with a pH adjuster.

  3. The abrasive slurry according to item 1 or 2, wherein the surfactant is contained within a range of 0.1 to 20% by mass.

  4). The cerium oxide concentration profile in the shell of the core-shell type abrasive particle has a concentration gradient in which the cerium oxide concentration increases from the interface region between the core and the shell toward the outermost surface region of the shell. 4. The abrasive slurry according to any one of items 1 to 3, wherein:

  5. The average content of cerium oxide in the outermost surface region of the core-shell type abrasive particles is in the range of 60 to 90% by mass, according to any one of items 1 to 4 The abrasive slurry described.

  6). 6. The abrasive slurry according to any one of items 1 to 5, wherein an average value of zeta potential of the core-shell type abrasive particles is within a range of −90 to −40 mV. .

  7). The average particle diameter of primary particles of the core-shell type abrasive particles is in the range of 0.02 to 2.00 μm, according to any one of items 1 to 6, Abrasive slurry.

  8). The core-shell type abrasive particles are characterized in that the ratio of spherical particles to the total number of core-shell type abrasive particles in the abrasive slurry is 80% by number or more. The abrasive slurry according to any one of the above.

  9. From the first item, the primary particle ratio (particle%) of the core-shell type abrasive particles is 85% or more within a pH range of 3.0 to 11.0 in terms of 25 ° C. The abrasive slurry according to any one of Items 8 to 8.

  By the above means of the present invention, the amount of cerium oxide used is suppressed, the abrasive particles do not agglomerate, the dispersion stability is excellent, the scratch resistance at the time of polishing is excellent, and an abrasive slurry having a high polishing rate is obtained. be able to.

Schematic diagram showing the structure of the core-shell type abrasive particles according to the present invention The schematic diagram which shows an example of the manufacturing process flow of the core-shell type abrasive | polishing material particle which concerns on this invention The graph which shows an example of the composition ratio of the element in the process in which the abrasive | polishing material particle of the core-shell type | mold which concerns on this invention and the composition of a shell changes continuously, and forming abrasive | polishing material particle The graph which shows another example of the composition ratio of the element in the process in which the abrasive particle of the core-shell type | mold which concerns on this invention, and the composition of a shell changes continuously, and forms an abrasive particle The schematic diagram which shows another example of the manufacturing process flow of the core-shell type abrasive particle which concerns on this invention The graph which shows an example of the composition ratio of the element in the process in which the abrasive particle of the core-shell type and the shell composition according to the present invention has a constant metal concentration and the abrasive particle is formed The graph which shows another example of the composition ratio of the element in the process in which the abrasive composition particles of the core-shell type and the shell composition according to the present invention are formed, and the abrasive particles are formed. An example of a photograph near the center of a particle obtained by performing cross-section processing on a core-shell type abrasive particle having a structure in which the composition of the shell according to the present invention continuously changes An example of the result of elemental analysis in the vicinity of the particle center obtained by performing cross-section processing on the core-shell type abrasive particles having a configuration in which the shell composition according to the present invention is continuously changed Example of scanning micrograph of core / shell type abrasive particles according to the present invention

  The abrasive slurry of the present invention is an abrasive slurry containing core / shell type abrasive particles each having a core and a shell having different compositions, and the core of the core / shell type abrasive particles has the following metal elements: An oxide of at least one metal element selected from the group as a main component, and the shell includes cerium oxide as a main component and an oxide of at least one metal element selected from the metal element group as a subcomponent. And the core and the shell contain at least one oxide (including cerium oxide) of the same metal element, and the particle size distribution of the core-shell type abrasive particles represented by the above formula (1) The coefficient of variation is 20% or less, and the average value of the zeta potential of the core-shell type abrasive particles is in the range of −120 to −30 mV. This feature is a technical feature common to the inventions according to claims 1 to 9.

  The core-shell type abrasive particles contained in the abrasive slurry of the present invention can form core particles with extremely high monodispersity by forming an oxide of a specific metal element as a main component as a core. . Further, as a method of coating the shell on the core particle, the cerium oxide having excellent polishing ability is the main component, and the core and the shell are formed by the presence of the same kind of metal element oxide (including cerium oxide). Thus, the crystal growth of the core and the shell can be stably performed, and abrasive particles having extremely high monodispersity and excellent polishing ability can be obtained. Such highly monodispersed particles are likely to agglomerate in the abrasive slurry, and due to the aggregation, the inherent properties of the particles cannot be fully exhibited, and the generation of scratches and loss of flatness due to the aggregates. It will cause a loss.

  In the present invention, the zeta potential of the core / shell type abrasive particles in the abrasive slurry is set to −120 to −30 mV from the viewpoint of sufficiently exhibiting the characteristics of such highly monodisperse core / shell type abrasive particles. By controlling within the range, the core-shell type abrasive particles are prevented from agglomerating in the polishing process, the core-shell type abrasive particles do not agglomerate, have excellent dispersion stability, and scratch resistance during polishing And an abrasive slurry having a high polishing rate can be obtained.

  By setting the zeta potential of the core-shell type abrasive particles according to the present invention to -30 mV or less, aggregation of the core-shell type abrasive particles in the polishing step can be prevented, and excellent scratch resistance at the time of polishing can be obtained. Can be obtained. Further, if the zeta potential is −120 mV or more, the repulsive force with the glass substrate which is the object to be polished and the surface is negatively charged can be suppressed, efficient polishing can be performed, and sufficient polishing speed can be achieved. Can be obtained.

  The range of the zeta potential of the core-shell type abrasive particles according to the present invention is preferably in the range of −90 to −40 mV from the viewpoint of further manifesting the above effects.

  As an embodiment of the present invention, from the viewpoint of manifestation of the effect of the present invention, the pH in terms of 25 ° C. of the abrasive slurry is adjusted within a range of 3.0 to 11.0 with a pH adjuster. preferable. By setting such a pH range, the core / shell type abrasive particles in the abrasive slurry can exist in a stable state, and damage to the core / shell type abrasive particles due to strong acid or strong alkali is caused. Can be prevented.

  Moreover, it is preferable to contain surfactant within the range of 0.1-20 mass%. By adding a surfactant to the abrasive slurry, the zeta potential of the core-shell type abrasive particles in the abrasive slurry can be adjusted to the desired zeta potential, and polishing with excellent particle dispersion stability A material slurry can be obtained.

  Further, the cerium oxide concentration profile in the shell of abrasive particles has a concentration gradient in which the cerium oxide concentration increases from the interface region between the core and the shell toward the outermost surface region of the shell, or polishing. The average content of cerium oxide in the outermost surface region of the material particles is preferably in the range of 60 to 85% by mass. By adopting such a shell configuration in which the composition changes continuously, the crystal growth from the core to the shell can be stably grown without causing distortion or defects in the crystal structure, and contributes to the polishing ability. Cerium oxide can be efficiently disposed on the outermost surface region while reducing the amount used, and an excellent polishing rate can be achieved.

  The core-shell type abrasive particles have an average primary particle diameter in the range of 0.02 to 2.00 μm, and the core-shell type abrasive particles have a ratio of 80 spherical particles. % Or more, and the primary particle ratio (particle%) of the core / shell type abrasive particles is 85% or more within a pH range of 3.0 to 11.0 in terms of 25 ° C. This is a preferred embodiment from the viewpoint of obtaining stable particles.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

《Abrasive particle structure》
The core / shell type abrasive particles according to the present invention are core / shell type abrasive particles each having a core and a shell having different compositions, and the cores are Ti, Sr, Y, Ba, Sm, Eu, Gd. And at least one metal element oxide selected from Tb as a main component, and the shell is composed of cerium oxide as a main component and at least one metal element selected from the metal element group constituting the core as a sub component. The core and the shell contain at least one oxide of the same metal element (including cerium oxide). In the present invention, the main component in the core or shell is defined as a state in which the content ratio of the metal element is 55 atomic% or more with respect to the total element ratio (number of atomic%), preferably 70% or more. It is. In addition, the subcomponent is defined as a state in which the content ratio of the metal element is less than 45 atomic% with respect to the total element ratio (number of atomic%).

  Hereinafter, the structure of the abrasive particles according to the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic diagram showing the structure of core / shell type abrasive particles according to the present invention (hereinafter also simply referred to as abrasive particles according to the present invention).

  The core-shell type abrasive particle A having a core and a shell according to the present invention is a core 1 (hereinafter referred to as an inner core part or a core part) constituting the inside including the central part of the core-shell type abrasive particle A. And an inorganic crystal particle having a crystal structure composed of a shell 2 (hereinafter also referred to as a shell layer) constituting an outer shell portion (also referred to as an “outermost layer”) of the abrasive particles.

  The core 1 may have a multilayer structure having a plurality of layers. In addition, even if the boundary line serving as the interface between the core 1 and the shell 2 is clearly separated as shown in FIGS. 1, 5A and 5B, the core as shown in FIGS. 3A and 3B. The constituent components of 1 and the constituent components of the shell 2 may be mixed in the vicinity of the boundary and the boundary line may be unclear.

  Elemental analysis of abrasive particles composed of a core and a shell according to the present invention is obtained by subjecting the obtained abrasive particles to cross-section processing using a focused ion beam (FB-2000A) manufactured by Hitachi High-Technologies, and passing through the vicinity of the particle center. Was cut out. From the cut surface, elemental analysis can be performed using Hitachi High-Technologies STEM-EDX (HD-2000) to evaluate the distribution of the particle composition.

(Particle profile)
As the elemental composition profile of the abrasive particles according to the present invention, the core according to the present invention is composed mainly of an oxide of at least one metal element selected from the metal element group. It is composed of cerium oxide as a component, and further composed of an oxide of at least one metal element selected from the metal element group used for the structure of the core as a subcomponent. Further, the core and the shell are characterized by containing at least one oxide (including cerium oxide) of the same metal element.

  The configuration of the abrasive particles is not particularly limited as long as the above conditions are satisfied, but the abrasive particles having the following configuration are more preferable.

  A typical first particle profile is a configuration in which the core is formed with a uniform composition in the entire region, and the composition of the shell continuously changes from the core interface toward the outermost surface region of the shell. Such a particle profile is referred to as Type A.

  A typical second particle profile has a structure in which the core is formed with a uniform composition in the entire region as in Type A, and the shell is formed with a uniform composition in the entire region as well. Such a particle profile is referred to as Type B.

  Hereinafter, as a representative profile of abrasive particles, an example of abrasive particles composed of yttrium oxide as an oxide of at least one metal element selected from a metal element group and cerium oxide as a main component forming a shell will be described as an example. To do.

(Type A abrasive particles)
The type A in which the composition of the shell continuously changes from the core interface toward the outermost surface region of the shell will be described later in detail, but as shown in FIG. 2, the core forming step A, the shell forming step B, manufactured through a solid-liquid separation step C and a firing step D.

  3A and 3B show typical element profiles of abrasive particles produced by the production flow shown in FIG.

  FIG. 3A is a profile of the composition ratio of elements in the course of forming abrasive particles with the abrasive particles having a core-shell type and a composition in which the shell composition continuously changes according to the present invention. 3 is the yttrium element ratio% (atomic number%) with respect to the total element concentration (yttrium + cerium), and 4 is the cerium element ratio% (atomic number%) with respect to the total element concentration (yttrium + cerium). This display is common in FIGS. 3B, 5A and 5B.

  As a profile of the element composition ratio shown in FIG. 3A, in the core formation step A, the cerium element is not supplied, but only the yttrium element is supplied to form a core having an yttrium oxide element ratio of 3%. . Subsequently, a solution containing yttrium element: cerium element at a ratio of 30:70 (molar ratio) is continuously supplied in the shell formation step B, and the yttrium element ratio 3 (atomic%) continuously from the interface between the core and the shell. The cerium element ratio (atomic%) 4 continuously increases, and finally, abrasive particles having a surface composition of 30% yttrium oxide and 70% cerium oxide are formed.

  FIG. 3B shows an example in which the core is formed at a ratio of 80% for the yttrium oxide element ratio 3 and 20% for the cerium oxide element ratio 4 instead of yttrium oxide alone (100%). is there.

  The abrasive particles having the profile of FIG. 3B are more stable than the abrasive particles having the profile of FIG. 3A, although the ratio of the cerium element in the entire particle is high, but the composition change width between the core and the shell is small. Particle formation and stress relaxation received on the particle surface can be performed more smoothly.

  In the abrasive particles according to the present invention, as shown in FIGS. 3A and 3B, the core and the shell are configured to contain at least one oxide of the same metal element (including cerium oxide). Features. That is, in FIG. 3A, yttrium oxide is a common oxide, and in FIG. 3B, yttrium oxide and cerium oxide are common oxides.

(Type B abrasive particles)
Type B, in which the core and shell are formed with a uniform composition in the entire region, will be described in detail later, but as shown in FIG. 4, the core formation step A, the solid-liquid separation step C1, the shell formation It is manufactured through a process B, a solid-liquid separation process C2, and a baking process D.

  Representative element profiles of abrasive particles produced by the production flow shown in FIG. 4 are shown in FIGS. 5A and 5B.

  FIG. 5A is a graph showing a profile of abrasive particles in which the composition of the core and shell is composed of a constant metal element concentration in the core-shell type abrasive particles according to the present invention.

  As a profile of the composition ratio of the elements shown in FIG. 5A, in the core formation step A, the cerium element is not supplied, but only the yttrium element is supplied to form a core having 100% yttrium oxide in the entire core area. . Next, the core (core particles) once formed is separated in the solid-liquid separation step C1, and after removing excess yttrium components, the hydrated water is added. In the shell formation step B, the yttrium element: cerium element is 30:70 (molar ratio). A solution containing the same is supplied to form a shell having a uniform composition with an yttrium element ratio 3 (atomic number%) of 30% and a cerium element ratio 4 (atomic number%) of 70% from the interface between the core and shell to the shell surface. To do.

  FIG. 5B shows an example in which the core is formed at a uniform ratio in the entire region of 80% yttrium oxide and 20% cerium oxide, instead of yttrium oxide alone (100%), compared to FIG. 5A. .

  In the abrasive particles according to the present invention, as shown in FIGS. 5A and 5B, the core and the shell are configured to contain at least one oxide of the same metal element (including cerium oxide). Features. That is, in FIG. 5A, yttrium oxide is a common oxide, and in FIG. 5B, yttrium oxide and cerium oxide are common oxides.

[Core material]
In the abrasive particles according to the present invention, the core is mainly composed of an oxide of at least one metal element selected from the following metal element group.

Metal element group: Ti (titanium), Sr (strontium), Y (yttrium), Ba (barium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium)
In the present invention, “mainly composed of an oxide of at least one metal element selected from the group of metal elements” means that the ratio of the oxide of the metal element to the total element ratio (number of atoms) constituting the core is , 55% or more, preferably 70% or more.

  In the formation of the core, the metal element is supplied in the form of a salt. For example, nitrates, hydrochlorides, sulfates, and the like can be used, but it is preferable to use nitrates with less contamination of the core.

  In the present invention, among the metal element group, the main metal elements include yttrium (yttrium oxide), samarium (samarium oxide), europium (europium oxide), gadolinium (gadolinium oxide), and terbium (terbium oxide). More preferably.

  As the oxide of the metal element constituting the core, two or more of the above metal element oxides may be used in combination, and cerium may be used in combination, but preferably, as shown in FIG. 3B or FIG. 5B The main component is composed of yttrium oxide, and the subcomponent includes cerium oxide. The ratio of cerium oxide in the core is preferably in the element concentration range of 5 to 30%.

[Component materials of shell]
The shell according to the present invention is characterized by containing cerium oxide as a main component and an oxide of at least one metal atom selected from the metal atom group as a subcomponent. The main component referred to in the present invention means that the constituent ratio of cerium oxide in the shell is 55% or more, preferably in the range of 60 to 90%, and more preferably in the range of 60 to 85%. It is.

  As described above, the shell according to the present invention has a concentration gradient in which the cerium oxide concentration increases from the interface region with the core toward the outermost surface region of the shell, as shown in FIGS. 3A and 3B. Even if it is A, as shown in FIG. 5A and FIG. 5B, it may be type B which has a uniform element concentration throughout the shell, but it is efficient to use monodispersity of particles, continuity of composition, and amount of cerium used. Type A is more preferable from the viewpoint of reducing the cost.

  Further, whether it is type A or type B, the average content (number of atoms) of cerium oxide in the outermost surface region of the particles is preferably in the range of 60 to 90%. The average content rate (number of atoms%) of subcomponents is in the range of 10 to 40%.

  The outermost surface region of the particle in the present invention refers to a region from the outermost surface to 5% by mass in the depth direction out of the total mass constituting the abrasive particle, and the cerium oxide in the components constituting this region. Expressed as average content.

  The shell according to the present invention is characterized in that the subcomponent is an oxide of at least one metal element selected from Ti, Sr, Y, Ba, Sm, Eu, Gd and Tb. Is yttrium.

  Moreover, the average content (number of atoms%) of the subcomponents in the shell is generally in the range of 10 to 45%, and preferably in the range of 10 to 40%.

[Elemental analysis of abrasive particles]
Elemental analysis of abrasive particles composed of a core and a shell according to the present invention is obtained by subjecting the obtained abrasive particles to cross-section processing using a focused ion beam (FB-2000A) manufactured by Hitachi High-Technologies, and passing through the vicinity of the particle center. Was cut out. From the cut surface, elemental analysis can be performed using Hitachi High-Technologies STEM-EDX (HD-2000) to evaluate the distribution of the particle composition. As an example, FIG. 7 shows an elemental analysis result of abrasive particles in which the ratio of cerium oxide in the shell shown in FIG. 3A according to the present invention is continuously changed. With respect to the cross section of the abrasive particles shown in FIG. 7, it can be confirmed that the ratio of cerium near 0.05 μm and 0.6 μm near the surface of the abrasive particles is high.

<Characteristic values of abrasive slurry and abrasive particles>
The abrasive slurry of the present invention is constituted by dispersing abrasive particles (dispersoid) having the above-described element profiles in a medium (dispersion medium). The concentration of the abrasive particles in the abrasive slurry of the present invention cannot be generally defined by setting the required polishing accuracy or polishing rate, but is generally in the range of 0.5 to 30% by mass. More preferably, it is in the range of 1.0 to 20% by mass, and particularly preferably in the range of 2.0 to 10% by mass.

  As a medium (dispersion medium), water is mainly used to constitute an aqueous dispersion. In addition, it is preferable to add a surfactant, a pH adjuster and the like to the abrasive slurry.

[Zeta potential]
In the abrasive slurry of the present invention, the above-described abrasive particles according to the present invention are present in a controlled manner within the range of −120 to −30 mV as the average value of the zeta potential in the medium. .

  The zeta potential in the present invention can be explained as follows.

  When the abrasive particles are present in a dispersed state in the dispersion medium, an electric double layer is formed between the abrasive particles and the dispersion medium. In the abrasive particles, there is an ion-fixed layer (also referred to as an adsorption layer) to which ions having the opposite charge to the surface of the abrasive particles are fixed, and on the outside, the charge between the fixed layer and the medium is neutralized. In this form, the ion diffusion layer is formed, and the potential of the ion diffusion layer is referred to as a zeta potential and is usually expressed in mV.

  The average value of the zeta potential of the abrasive particles in the abrasive slurry of the present invention is in the range of −120 to −30 mV, and more preferably in the range of −90 to −40 mV.

  As described above, the characteristics of the core-shell type abrasive particles according to the present invention are extremely excellent in monodispersity, and as a result, have high polishing ability and can impart uniform polishing performance. In order to achieve the maximum effect, it is important to control the agglomeration of abrasive particles severely.

  As a result of earnestly examining the conditions under which the characteristics of the abrasive particles according to the present invention having excellent characteristics can be fully exhibited, the present inventors have determined the zeta potential of the abrasive particles in the abrasive slurry. As an average value, control within the range of −120 to −30 mV suppresses the aggregation of abrasive particles in the abrasive slurry, and reduces the polishing ability (polishing rate) even when used for a long time. An abrasive slurry excellent in stability could be obtained without waking up.

  As described above, if the zeta potential of the abrasive particles in the abrasive slurry is -30 mV or less, the abrasive particles are excellent in agglomeration in the abrasive slurry even when used for a long period of time. Dispersion stability can be realized in the abrasive particles, and generation of polishing scratches and the like during polishing by the aggregate can be suppressed. Moreover, if the zeta potential of the abrasive particles is −120 mV or more, many glass substrate surfaces are negatively charged, and excessive electrical repulsion between the abrasive particles and the glass substrate surface can be suppressed. As a result, a sufficient polishing rate can be achieved.

  In the abrasive slurry of the present invention, the method for applying the zeta potential defined in the present invention to the abrasive particles present in the dispersion medium is not particularly limited. For example, when preparing the abrasive slurry In addition, a desired zeta potential can be obtained by appropriately selecting the surfactant having the optimum characteristics, adjusting the addition amount, adding an additive having a charge, and setting the pH value of the abrasive slurry. Can do.

  The zeta potential according to the present invention can be measured using, for example, an electrophoretic Doppler method using a nano particle analyzer “HORIBA nano Partica SZ-100 (manufactured by Horiba, Ltd.)”. In the measurement, the zeta potential of 500 or more abrasive fine particles can be measured and obtained from the arithmetic average value.

  Specifically, a dispersion medium whose pH is adjusted with an acid or a base so as to have a pH equivalent to the abrasive slurry to be used, or a medium solution in which abrasive particles are separated from the abrasive slurry are used. Then, a 5.0 mass% abrasive slurry is diluted 1000 times, and the zeta potential is measured with respect to 500 or more particles using the diluted solution, and obtained from the arithmetic average value.

[Coefficient of variation of particle size distribution]
In the present invention, the abrasive particles according to the present invention are excellent in monodispersity, and the narrow particle size distribution is an important feature of the particles. Specifically, the coefficient of variation of the particle size distribution of the abrasive particles is It is characterized by being 20% or less, more preferably 15% or less. The lower limit is desirably 0%, but is practically 1% or more.

  The coefficient of variation of the particle size distribution referred to in the present invention can be determined according to the following method.

  A scanning micrograph (SEM image) is taken for the target abrasive particles, and the particle diameter is measured for about 100 particles. The particle diameter referred to in the present invention is represented by the diameter when it is circular, and if it is an irregular shape other than circular, the projected area is converted into a circle equivalent and displayed as the diameter at that time.

  Next, the arithmetic average particle diameter (μm) of 100 abrasive particles is obtained, and the standard deviation of the particle diameter distribution is further obtained based on the data.

  Next, the coefficient of variation (%) of the particle size distribution can be determined according to the following equation from the average particle size (μm) of the abrasive particles determined by the above measurement and the standard deviation of the particle size distribution.

Coefficient of variation of particle size distribution (%) = (standard deviation of particle size distribution / average particle size) × 100
If the coefficient of variation (%) in the particle size distribution is 20% or less, it is an abrasive particle with an extremely narrow particle size distribution, and when abrasive slurry is prepared, variation in abrasiveness due to particle size variation is suppressed. And uniform polishing can be performed.

[PH value]
In the abrasive slurry of the present invention, the pH in terms of 25 ° C. of the abrasive slurry is preferably adjusted within a range of 3.0 to 11.0 with a pH adjuster, more preferably 5. It is in the range of 0 to 9.0.

  By controlling the pH of the abrasive slurry of the present invention within the range specified above, the influence on the abrasive particles in a strongly acidic environment or a strongly alkaline environment can be suppressed. In addition, by setting the pH within the above range, the zeta potential of the abrasive particles defined in the present invention can be easily controlled within a desired range.

  The pH value according to the present invention can be determined by measuring at 25 ° C. using, for example, a Lacom tester desktop PH & conductivity meter (PH1500 manufactured by ASONE Corporation).

  In addition, as a pH adjuster used for adjusting the pH of the abrasive slurry to a desired pH value range, for example, hydrochloric acid, phosphoric acid, phosphate, citric acid, sodium citrate, adipic acid, sodium acetate, Sodium carbonate, sodium sulfite, sodium acetate, triethanolamine, sodium hydroxide and the like can be appropriately selected and used.

[Surfactant]
The abrasive slurry of the present invention preferably contains a surfactant from the viewpoint of adjusting the dispersion stability of the contained abrasive particles and the desired zeta potential, and the content is 0.1-20. It is preferably in the range of mass%, more preferably in the range of 0.2 to 10 mass%. If the content of the surfactant is 0.1% by mass or more, it can contribute to the dispersion stability of the abrasive particles, a zeta potential of −30 mV or less can be obtained, and if it is 20% by mass or less, A zeta potential of −120 mV or more can be obtained, and an adverse effect on the polishing performance by the surfactant can be eliminated.

  As the surfactant applied to the present invention, an anionic surfactant (anionic surfactant), a cationic surfactant (cationic surfactant), a nonionic surfactant (nonionic surfactant) Agents), betaine surfactants (amphoteric surfactants) and the like, and polymer dispersants and the like. Among them, the abrasive particle surface is negatively charged (the zeta potential is Therefore, it is preferable to select from the above surfactants and polymer dispersants excluding cationic surfactants (cationic surfactants).

  Examples of the anionic surfactant include fatty acid soap, N-acyl-N-methylglycine salt, N-acyl-N-methyl-β-alanine salt, N-acyl glutamate, alkyl ether carboxylate, acylation Peptide, alkyl sulfonate, alkyl benzene sulfonate, alkyl naphthalene sulfonate, dialkyl sulfosuccinate, alkyl sulfoacetate, α-olefin sulfonate, N-acylmethyl taurine, sulfated oil, higher alcohol sulfate Salts, secondary higher alcohol sulfates, alkyl ether sulfates, secondary higher alcohol ethoxy sulfates, polyoxyethylene alkylphenyl ether sulfates, monoglycolates, fatty acid alkylolamide sulfates, alkyl ether phosphoruss Examples include acid ester salts and alkyl phosphate ester salts.

  Examples of betaine surfactants include carboxybetaine type, sulfobetaine type, aminocarboxylate, imidazolinium betaine and the like.

  Nonionic surfactants include polyoxyethylene alkyl ether, polyoxyethylene secondary alcohol ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene sterol ether, polyoxyethylene lanolin derivative, polyoxyethylene polyoxypropylene alkyl ether, Examples include polyoxyethylene glycerin fatty acid ester.

  Further, in order to stably disperse the abrasive particles according to the present invention in the abrasive slurry, the following water-soluble resin can be used as the water-soluble polymer dispersant. As the water-soluble resin, styrene-acrylic acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid copolymer, styrene-maleic acid copolymer, styrene-maleic acid-acrylic acid alkyl ester copolymer are preferably used. Styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid half ester copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer It is a water-soluble resin such as.

  Examples of the anionic polymer dispersant preferably used in the present invention include polyvinyl alcohols, polyvinyl pyrrolidones, polyacrylic acid, acrylic acid-acrylonitrile copolymers, and potassium acrylate-acrylonitrile copolymers. , Acrylic resins such as vinyl acetate-acrylic acid ester copolymer, acrylic acid-acrylic acid ester copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid ester Copolymers, styrene-acrylic resins such as styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer, styrene-maleic acid copolymer, styrene- Maleic anhydride copolymer, vinyl naphthalene-acrylic Luric acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene copolymer, vinyl acetate-maleic acid ester copolymer, vinyl acetate-crotonic acid copolymer Examples include polymers, vinyl acetate copolymers such as vinyl acetate-acrylic acid copolymers, and salts thereof.

[Average particle size]
In the abrasive particles according to the present invention, the average particle diameter of the primary particles is preferably in the range of 0.10 to 2.00 μm.

  The average particle size according to the present invention can be determined by the same method as described for the coefficient of variation of the particle size distribution.

  In the abrasive particles according to the present invention, the average particle diameter of the core (core particles) is preferably in the range of 0.01 to 0.9 μm. By setting it within this range, it is possible to maintain high durability against pressure applied during polishing.

  Moreover, as thickness of a shell, the range of 0.005-0.55 micrometer is preferable. By setting it within this range, excellent monodispersity can be obtained, and core / shell type abrasive particles excellent in polishing rate and polishing uniformity can be prepared.

  The abrasive particles contained in the abrasive slurry differ in the required level for the average particle size depending on their use, but are included in the abrasive used as the surface finish accuracy of the polished glass substrate and the like increases. It is necessary to make the abrasive particles fine. For example, in order to use in the manufacturing process of a semiconductor device, it is preferable that an average particle diameter is 2.0 micrometers or less.

  On the other hand, the smaller the particle size of the abrasive particles, the higher the surface finish accuracy of the polished glass substrate and the like, but the polishing rate tends to be slower as the average particle size is smaller, and the lower limit is 0.02 μm. If the average particle diameter is 0.02 μm or more, it is possible to maintain the advantage that the polishing rate of the abrasive particles according to the present invention is higher than that of an abrasive such as colloidal silica.

  Therefore, the average particle diameter of the core-shell type abrasive particles according to the present invention is preferably in the range of 0.02 to 2.0 μm, and more preferably in the range of 0.05 to 1.5 μm.

[Shape of abrasive particles]
The shape of the abrasive particles according to the present invention is not particularly limited, and may be spherical, elliptical, rectangular, or indefinite, but can obtain a high degree of surface finish accuracy with respect to the substrate and can be used for a long time. From the viewpoint of excellent dispersion stability of abrasive particles even in the use of these abrasives, the abrasive particles preferably have a spherical particle ratio of 80% by number or more.

  The spherical particle as used in the present invention is a photomicrograph (SEM image) taken of abrasive particles, and has a circular shape, where a is the short axis and b is the short axis. If the value is in the range of 0.80 to 1.00, it is defined as a spherical particle.

[Primary particle ratio]
In the abrasive slurry of the present invention, the primary particle ratio (particle%) of the abrasive particles is preferably 85% or more, more preferably 90% or more, within a pH range of 3.0 to 11.0. It is.

  Take a scanning photomicrograph of the abrasive slurry (for example, Fig. 8) and measure the proportion of abrasive particles that are present individually and in the form of primary particles without causing aggregation (secondary particles or more). To do. With respect to this characteristic value, when the pH is in the range of 3.0 to 11.0, the generation of aggregates is extremely small, and scratches and the like on the substrate surface due to the aggregates during polishing can be prevented.

[Polishing speed]
The abrasive slurry of the present invention is composed of abrasive particles excellent in monodispersity and has a high polishing rate.

  In the present invention, the polishing rate (polishing rate) is preferably in the range of 0.30 to 0.80 μm / min.

  The polishing rate as referred to in the present invention can be determined by measuring, for example, according to the following method.

  The polishing machine used for polishing is a machine that polishes the surface to be polished with a polishing cloth while supplying abrasive slurry in which core / shell type abrasive particles are dispersed in a dispersion medium such as water to the surface to be polished. It is. The abrasive slurry has only a water dispersion medium and a concentration of 100 g / L.

  In the polishing test, polishing is performed by circulatingly supplying an abrasive slurry at a flow rate of 5 L / min. A 65 mmφ glass substrate is used as an object to be polished, and a polishing cloth made of polyurethane is used as the polishing cloth.

The polishing pressure on the polished surface is set to 9.8 kPa (100 g / cm ² ), the rotation speed of the polishing tester is set to 100 min ⁻¹ (rpm), and polishing is performed for 30 minutes. The thickness (μm) before and after polishing is measured by Nikon Digimicro (MF501), the polishing amount (μm) per minute is calculated from the thickness displacement, and the polishing rate (μm / min) can be obtained.

<< Production Method of Abrasive Particles >>
Next, a specific method for producing abrasive particles having the element profile described above will be described.

[Outline of production method of abrasive particles]
As described above, as a method for producing abrasive particles applicable to the present invention, type A abrasive particles (FIGS. 3A and 3B) that form a uniform core and a shell in which the composition changes continuously are used. Examples include a manufacturing method, and a manufacturing method of type B abrasive particles (FIGS. 5A and 5B) that form a uniform composition core and a uniform composition shell.

(Method for producing type A abrasive particles)
As shown in FIG. 2, the production method of type A abrasive particles according to the present invention is a production of an embodiment comprising four steps of a core formation step A, a shell formation step B, a solid-liquid separation step C, and a firing step D. This is a method for producing abrasive particles having an element profile as shown in FIG. 3A or 3B.

1. Core formation process A
The core formation step A is at least one selected from Ti (titanium), Sr (strontium), Y (yttrium), Ba (barium), Sm (samarium), Eu (europium), Gd (gadolinium), and Tb (terbium). The metal element salt is formed, and the core 1 of the precursor of the abrasive particles mainly composed of the salt of the element is formed.

Specifically, in the core forming step, for example, a yttrium salt and a precipitant are dissolved in water to prepare a solution having a predetermined concentration. The seed crystal of the core 1 is formed by heating and stirring the solution at 80 ° C. or higher. In the core formation step, a solution prepared with a yttrium salt is further added to the prepared solution, and the mixture is heated and stirred at 80 ° C. or higher. Thereby, the core forming step forms a basic carbonate insoluble in water, for example, yttrium basic carbonate (Y (OH) CO ₃ or Y (OH) CO ₃ .xH ₂ O, x = 1, etc.). Then, by growing yttrium basic carbonate on the outside of the seed crystal, it becomes the core 1 of the precursor of abrasive particles. In the following description, a solution that has started heating and stirring is referred to as a reaction solution.

  In the core formation step, selected from Ti (titanium), Sr (strontium), Y (yttrium), Ba (barium), Sm (samarium), Eu (europium), Gd (gadolinium) and Tb (terbium) dissolved in water As the salt of at least one kind of metal element, nitrate, hydrochloride, sulfate and the like can be used, but it is preferable to use nitrate with less contamination of the product.

  The precipitating agent may be any alkaline compound that produces a basic carbonate when mixed with water with the element salt and heated, and urea compounds, ammonium carbonate, ammonium hydrogen carbonate, and the like are preferable.

  Examples of urea compounds include urea salts (eg, nitrates and hydrochlorides), N, N'-dimethylacetylurea, N, N'-dibenzoylurea, benzenesulfonylurea, p-toluenesulfonylurea, trimethylurea, tetraethyl. Examples include urea, tetramethylurea, triphenylurea, tetraphenylurea, N-benzoylurea, methylisourea, and ethylisourea, and also contain urea. Of the urea compounds, urea is particularly preferable in that it is gradually hydrolyzed so that a precipitate is slowly generated and a uniform precipitate is obtained.

  Further, by forming a basic carbonate insoluble in water, for example, a basic carbonate of yttrium, the deposited precipitate can be dispersed in a monodispersed state. Furthermore, since a basic carbonate of cerium is also formed in the shell formation step described later, a continuous layer structure of basic carbonate can be formed.

  In the core formation step, for example, the addition rate of the aqueous solution containing yttrium is preferably within a range of 0.003 to 5.5 mol / L per minute, and it may be added to the reaction solution while heating and stirring at 80 ° C. or higher. preferable. This is because by setting the addition rate within the above range, spherical abrasive particles having excellent monodispersibility are easily formed.

  This is because the heated urea is easily stirred at 80 ° C. or higher so that decomposition of the added urea easily proceeds. Moreover, the concentration of urea to be added is preferably 5 to 50 times the concentration of ions of yttrium, for example. This is because it is possible to synthesize spherical abrasive particles exhibiting monodispersity by setting the ion concentration and urea concentration in the aqueous solution of yttrium within the ranges.

  If sufficient stirring efficiency is obtained during heating and stirring, the shape of the stirrer is not specified, but a rotor / stator type axial flow stirrer is used to obtain higher stirring efficiency. It is preferable to do.

2. Shell formation process B
The shell forming step B is performed continuously following the core forming step A.

  Hereinafter, an example in which the shell is formed using yttrium (III) nitrate and cerium (III) nitrate will be described.

For example, an aqueous solution prepared from yttrium nitrate (III) and cerium nitrate (III) is added to a reaction solution in which a basic carbonate of yttrium is dispersed for a predetermined time at a constant rate, and the basic yttrium is outside the core 1. Carbonates such as yttrium basic carbonates (Y (OH) CO ₃ or Y (OH) CO ₃ .xH ₂ O, x = 1 etc.) and cerium basic carbonates such as cerium basic carbonates ( A shell 2 of a precursor of abrasive particles containing Ce (OH) CO ₃ or Ce (OH) CO ₃ .xH ₂ O, x = 1 or the like) is formed.

  In addition, as the cerium salt used for the preparation of the aqueous solution, it is preferable to use a nitrate with less contamination of the product, so the case where cerium (III) nitrate is used is shown, but this is not a limitation. Hydrochloride, sulfate and the like can be used.

  The addition rate of the aqueous solution added in the shell forming step is preferably within a range of 0.003 to 5.5 mol / L per minute. This is because by setting the addition rate within the above range, spherical abrasive particles having excellent monodispersibility are easily formed.

  Moreover, it is preferable that the ratio of the density | concentration of the cerium which the aqueous solution to add contains is 85% or less. This is because, when the ratio of the cerium concentration in the aqueous solution to be added is greater than 85%, when the addition is performed for the same addition time as in the case of adding an aqueous solution prepared to 85% or less, the formed abrasive particles are monodispersed. This is because it does not show properties and tends to aggregate in a plate shape.

  The reaction solution is preferably heated and stirred at 80 ° C. or higher while the aqueous solution is added at the addition rate. This is because when heated and stirred at 80 ° C. or higher, decomposition of urea added in the core formation step A easily proceeds.

3. Solid-liquid separation process C
In the solid-liquid separation step C, the precursor of the core / shell type abrasive particles in which the shell 2 is formed in the shell formation step B is solid-liquid separated from the reaction solution. In the solid-liquid separation step C, the obtained core / shell type abrasive particle precursor may be dried and then transferred to the firing step D as necessary.

4). Firing step D
In the firing step D, the precursor of the core / shell type abrasive particles obtained in the solid-liquid separation step C is in the range of 500 to 1200 ° C. for 1 to 5 hours in air or in an oxidizing atmosphere. Bake with. Since the precursor of the core / shell type abrasive particles is calcined to release carbon dioxide, the basic carbonate is converted into an oxide, and the target core / shell type abrasive particles are obtained.

(Method for producing type B abrasive particles)
As shown in FIG. 4, the method for producing type B abrasive particles in which the core and the shell according to the present invention are both composed of a uniform composition comprises a core formation step A, a solid-liquid separation step C1, a shell formation step B, This is a method for producing abrasive particles having an element profile as shown in FIG. 5A or FIG. 5B by a production method comprising five steps of a solid-liquid separation step C2 and a firing step D.

1. Core formation process A
The core forming step A in type B is the same as the core forming step A in type A, and forms a core having a uniform composition as shown in FIG. 5A or 5B.

2. Solid-liquid separation process C1
In the solid-liquid separation step C1, the core (core particles) formed in the core formation step A is solid-liquid separated from the reaction solution and dried.

3. Shell formation process B
In the shell formation step B, the core (core particles) separated in the solid-liquid separation step C1 is redispersed in water or the like, and then a shell having a uniform composition is formed by the same method as the shell formation step B in type A. To do.

4). Solid-liquid separation process C2
The solid-liquid separation step C2 is performed by the same method as the solid-liquid separation step C in Type A.

5. Firing step D
The firing step D is performed by the same method as the firing step D in type A, and produces type B abrasive particles having a uniform composition core and a uniform composition shell.

《Abrasive slurry usage and abrasive deterioration》
Next, a method for using the abrasive slurry will be described by taking the polishing process of the glass substrate as an example.

1. Preparation of Abrasive Slurry Core / shell type abrasive particles are added to a solvent such as water to prepare an abrasive slurry. By adding a surfactant (also referred to as a dispersant) or the like to the abrasive slurry, aggregation is prevented and stirring is always performed using a stirrer or the like to maintain a dispersed state. The abrasive slurry is circulated and supplied to the polishing machine using a supply pump.

2. Polishing process The glass substrate is brought into contact with the upper and lower surface plates of the polishing machine to which the polishing pad (polishing cloth) is applied, and the pad and the glass are moved relative to each other under pressure while supplying the abrasive slurry to the contact surface. It is polished by that.

3. Abrasive Particle Degradation Abrasive particles are used under pressure as in the polishing step. For this reason, the core-shell type abrasive particles contained in the abrasive slurry gradually collapse and become finer as the polishing time elapses. Since miniaturization of the core / shell type abrasive particles causes a reduction in the polishing rate, core / shell type abrasive particles having a small change in particle size distribution before and after polishing are desired.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<< Preparation of abrasive particles >>
[Preparation of abrasive particles 1]
According to the following method, abrasive particles 1 having a structure in which the composition of the shell as shown in FIG. 3A continuously changes were prepared according to the steps shown in FIG.
(1) Core formation process A
After preparing 10 L of 0.01 mol / L yttrium nitrate (III) aqueous solution (hereinafter simply referred to as yttrium nitrate), urea was added to the yttrium nitrate aqueous solution so that the concentration of urea was 0.25 mol / L. After stirring, heating and stirring were started at 90 ° C.

A basic carbonate is added to the reaction solution obtained in a) above by adding a 1.0 mol / L yttrium nitrate aqueous solution at a rate of 1.0 mL / min for 60 minutes while heating and stirring at 90 ° C. Dispersion 1A containing core particles consisting of was prepared.
(2) Shell formation process B
1.0 mol / L cerium nitrate (III) (1.0 mol / L) was added to the dispersion 1A containing core particles prepared in (1) above at an addition rate of 0.30 mL / min. Hereinafter, it is simply referred to as cerium nitrate.) A precursor of abrasive particles in which an aqueous solution is simultaneously added at 90 ° C. for 60 minutes at an addition rate of 0.70 mL / min to form a shell on the core particles. Dispersion 1B containing was prepared.
(3) Solid-liquid separation process C
Dispersion 1B containing the abrasive particle precursor prepared in (2) above was separated into an abrasive particle precursor and a solution (dispersion medium) using a membrane filter.
(4) Firing step D
The abrasive particle precursors separated in (3) above were fired at 600 ° C. to obtain core / shell type abrasive particles 1 having the elemental profile shown in FIG. 3A.

[Preparation of abrasive particles 2]
In the preparation of the abrasive particles 1, (1) the core forming step A was changed to the following conditions, and the core portion as shown in FIG. 3B was composed of yttrium oxide and cerium oxide, and the composition of the shell Abrasive material particles 2 having a structure in which the thickness continuously changes were prepared.
(1) Core formation process A
a) After preparing 10 L of an aqueous solution containing 0.008 mol / L yttrium nitrate and 0.002 mol / L cerium nitrate, the urea was added to the yttrium nitrate aqueous solution so that the concentration of urea was 0.25 mol / L. After sufficiently stirring, heating and stirring were started at 90 ° C.

  b) To the reaction solution obtained in a) above, 0.7 mol / L yttrium nitrate aqueous solution was added at a rate of 1.0 mL / min, and 0.3 mol / L cerium nitrate aqueous solution was added at 1.0 mL / min. A dispersion 2A containing a core 1 composed of a basic carbonate was prepared by simultaneous addition for 60 minutes while heating and stirring at 90 ° C. at a speed.

[Preparation of abrasive particles 3]
According to the following method, abrasive particles 3 having a uniform composition of the core and shell as shown in FIG. 5A in the entire region were prepared according to the steps shown in FIG.
(1) Core formation process A
a) After preparing 10 L of 0.01 mol / L yttrium nitrate aqueous solution, adding it to this yttrium nitrate aqueous solution so that the concentration of urea is 0.25 mol / L, stirring sufficiently, and then heating and stirring at 90 ° C. Started.

b) To the reaction solution obtained in a) above, 1.0 mol / L yttrium nitrate aqueous solution was added at a rate of 1.0 mL / min for 60 minutes while heating and stirring at 90 ° C. Dispersion 3A containing core particles made of carbonate was prepared.
(2) Solid-liquid separation process C1
The dispersion 3A containing the core particles prepared in the above (1) was separated into a core particle and a solution (dispersion medium) using a membrane filter.
(3) Shell formation process B
An aqueous solution containing 0.003 mol / L yttrium nitrate and 0.007 mol / L cerium nitrate after the core particles separated in (2) above are uniformly dispersed in 10 L of pure water in a primary particle state using a homogenizer. After adding urea so that it might become a density | concentration of 0.25 mol / L and stirring sufficiently, heating stirring was started at 90 degreeC.

Next, with respect to the aqueous solution, a 1.0 mol / L yttrium nitrate aqueous solution was added at a rate of 0.3 mL / min, and a 1.0 mol / L cerium nitrate aqueous solution was added at a rate of 0.7 mL / min. A dispersion 3B containing a precursor of abrasive particles in which a shell was formed on the core particles was simultaneously added for 60 minutes while stirring at 0 ° C. with stirring.
(4) Solid-liquid separation process C2
The dispersion liquid 3B containing the abrasive particle precursor prepared in (3) above was separated into an abrasive particle precursor and a solution (dispersion medium) using a membrane filter.
(5) Firing step D
The precursor of the abrasive particles separated in (4) above was fired at 600 ° C. to obtain core / shell type abrasive particles 3 having the element profile shown in FIG. 5A.

[Preparation of abrasive particles 4]
In the preparation of the abrasive particles 3, (1) the core forming step A was changed to the following conditions, and the core portion as shown in FIG. 5B was composed of yttrium oxide and cerium oxide, and the shell was uniform. Abrasive particles 4 having the composition were prepared.
(1) Core formation process A
a) After preparing 10 L of an aqueous solution containing 0.008 mol / L yttrium nitrate and 0.002 mol / L cerium nitrate, urea is added to the yttrium nitrate / cerium nitrate mixed aqueous solution so that the concentration of urea is 0.25 mol / L. After stirring sufficiently, heating and stirring were started at 90 ° C.

  b) To the reaction solution obtained in the above a), 1.0 mol / L yttrium nitrate aqueous solution was added at a rate of 0.3 mL / min, and 1.0 mol / L cerium nitrate aqueous solution was added to 0.7 mL / min. A dispersion 4A containing a precursor of abrasive particles in which a shell was formed on the core particles was simultaneously added at 90 ° C. with heating and stirring at 90 ° C.

[Preparation of abrasive particles 5]
(1) 10 L of water was prepared, urea was added so as to have a concentration of 0.20 mol / L, and after stirring sufficiently, the mixture was heated and stirred until it reached 90 ° C.
(2) A 1.0 mol / L yttrium nitrate aqueous solution is added to the urea aqueous solution obtained in (1) above at a rate of 0.5 mL / min, and 1.0 mol / L cerium nitrate aqueous solution is added to 0.5 mL. A dispersion 5A containing a precursor of abrasive particles having a single composition was prepared by simultaneously adding 120 minutes while heating and stirring at 90 ° C. at an addition rate of / min.
(3) Abrasive particle precursors are separated from the dispersion 5A obtained in the above (2) by a membrane filter, and the separated abrasive particle precursors are baked at 600 ° C. to obtain 50% cerium oxide. Then, abrasive particles 5 composed of one layer composed of 50% yttrium oxide were obtained.

[Preparation of abrasive particles 6]
(1) 10 L of water was prepared, and urea was added to this water so as to have a concentration of 0.20 mol / L. After sufficient stirring, heating and stirring were started at 90 ° C.
(2) To the reaction solution obtained in (1) above, 1.0 mol / L yttrium nitrate aqueous solution was added at a rate of 1.0 mL / min for 110 minutes while heating and stirring at 90 ° C. A dispersion 6A containing particles was prepared.
(3) To the dispersion 6A containing the core particles obtained in (2) above, a 1.0 mol / L cerium nitrate aqueous solution is heated and stirred at 90 ° C. for 10 minutes at an addition rate of 1.0 mL / min. It was added to form a shell to prepare a dispersion 6B containing a precursor of abrasive particles.
(4) Abrasive particles are separated from the dispersion liquid 6B obtained in (3) above by a membrane filter and fired at 600 ° C., and the core is made of yttrium oxide and the shell is made of cerium oxide. Material particles 6 were prepared.

[Preparation of abrasive particles 7]
In the preparation of the abrasive particles 4 described above, (1) b) of the core forming step A was performed in the same manner except that the concentration of the aqueous yttrium nitrate solution and the aqueous cerium nitrate solution was changed to 10 times as follows. A wide (coefficient of variation: 136%) abrasive particles 7 were prepared.

  b) A 10.0 mol / L cerium nitrate aqueous solution was added to the reaction solution containing the seed crystals obtained in a) above at a rate of addition of 10.0 mol / L yttrium nitrate aqueous solution at 0.8 mL / min. A dispersion 7A containing a core composed of a basic carbonate was prepared by simultaneous addition for 60 minutes while heating and stirring at 90 ° C. at an addition rate of 0.2 mL / min.

[Preparation of abrasive particles 8]
In the preparation of the abrasive particles 4 described above, (3) the shell formation step B was performed in the same manner except that the concentrations of the yttrium nitrate aqueous solution and the cerium nitrate aqueous solution were changed to 10 times as described below. (Coefficient: 148%) Abrasive particles 8 were prepared.
(3) Shell formation process B
An aqueous solution containing 0.003 mol / L yttrium nitrate and 0.007 mol / L cerium nitrate after the core particles separated in (2) above are uniformly dispersed in 10 L of pure water in a primary particle state using a homogenizer. After adding urea so that it might become a density | concentration of 0.25 mol / L, after fully stirring, it heated and stirred at 90 degreeC for 1 hour.

  Next, with respect to the aqueous solution, a 10.0 mol / L yttrium nitrate aqueous solution was added at a rate of 0.3 mL / min, and a 10.0 mol / L cerium nitrate aqueous solution was added at a rate of 0.7 mL / min. A dispersion 8B containing a precursor of abrasive particles in which a shell was formed on the core particles was simultaneously added for 60 minutes while stirring at 0 ° C. with stirring.

[Preparation of abrasive particles 9]
In the preparation of the abrasive particles 3, abrasive particles 9 were prepared in the same manner except that gadolinium (III) nitrate was used instead of yttrium (III) nitrate as the metal element used for forming the core. The abrasive particles 9 have a configuration that does not include a metal element that is common to the core and the shell.

[Preparation of abrasive particles 10]
In the preparation of the abrasive particles 2, the addition rate of the 1.0 mol / L yttrium nitrate aqueous solution in (2) shell formation step B was 0.40 mL / min, and the addition rate of the 1.0 mol / L cerium nitrate aqueous solution was 0. Abrasive particle 10 was prepared in the same manner except that it was changed to 60 mL / min.

[Preparation of abrasive particles 11]
In the preparation of the abrasive particles 2, (2) the addition rate of the 1.0 mol / L yttrium nitrate aqueous solution in the shell formation step B was 0.15 mL / min, and the addition rate of the 1.0 mol / L cerium nitrate aqueous solution was 0. Abrasive particle 11 was prepared in the same manner except that it was changed to .85 mL / min.

[Preparation of abrasive particles 12]
In the preparation of the abrasive particles 2, (2) the addition rate of the 1.0 mol / L yttrium nitrate aqueous solution in the shell formation step B was 0.10 mL / min, and the addition rate of the 1.0 mol / L cerium nitrate aqueous solution was 0. Abrasive particles 12 were prepared in the same manner except for changing to 90 mL / min.

[Measurement of characteristics of abrasive particles]
(Measurement of cerium concentration in the outermost surface area of particles)
Each abrasive particle was subjected to cross-section processing using a focused ion beam (FB-2000A) manufactured by Hitachi High-Technologies, and a surface passing through the vicinity of the particle center was cut out. From the cut surface, elemental analysis was performed using STEM-EDX (HD-2000) manufactured by Hitachi High-Technologies, and the average cerium concentration from the outermost surface portion of the particles to a region of 5% in the depth direction was measured.

(Measurement of average particle size)
A scanning micrograph (SEM image) was taken for each of the prepared abrasive particles, and the particle diameter of about 100 particles was measured. If the target particle is spherical, it is represented by its diameter, and if it is an irregular shape other than spherical, its projected area is converted into a circle equivalent and displayed as the diameter at that time. Subsequently, the arithmetic average particle diameter (micrometer) of 100 measured abrasive particles was calculated | required, and this was made into the average particle diameter.

(Particle shape)
Scanning micrographs (SEM images) of each of the prepared abrasive particles were taken and had a circular shape. When the minor axis was a and the major axis was b, the value of a / b was 0. If it was in the range of 80 to 1.00, it was defined as a spherical particle, and the others were classified as amorphous.

(Measurement of variation coefficient of particle size distribution)
A scanning micrograph (SEM image) was taken for each of the prepared abrasive particles, and the particle diameter of about 100 particles was measured. If the target particle is spherical, it is represented by its diameter, and if it is an irregular shape other than spherical, its projected area is converted into a circle equivalent and displayed as the diameter at that time. Subsequently, the arithmetic average particle diameter (micrometer) of 100 measured abrasive particles was calculated | required, and also the standard deviation of particle diameter distribution was computed based on the data.

  Next, the coefficient of variation (%) of the particle size distribution was determined from the average particle size (μm) of the abrasive particles determined by the above measurement and the standard deviation of the particle size distribution according to the following formula.

Coefficient of variation of particle size distribution (%) = (standard deviation of particle size distribution / average particle size) × 100
Table 1 shows the configuration of each abrasive particle prepared as described above and the measurement results obtained.

<< Preparation of abrasive slurry >>
[Preparation of abrasive slurry 1]
After the following constituent materials were mixed, a dispersion treatment was performed with a homogenizer to prepare an abrasive slurry 1.

Abrasive particles 1 (average particle size: 0.56 μm, coefficient of variation of particle size distribution: 14%)
5.0 parts by mass Pure water 95.0 parts by mass [Preparation of abrasive slurry 2]
After the following constituent materials were mixed, a dispersion treatment was performed with a homogenizer to prepare an abrasive slurry 2.

Abrasive particles 1 (average particle size: 0.56 μm, coefficient of variation of particle size distribution: 14%)
5.0 parts by mass Surfactant (polymer dispersant: Polyty A550, acrylic acid-maleic acid copolymer, manufactured by Lion Corp.) 0.15 parts by mass Pure water 94.8 parts by mass [Abrasive slurry 3 to Preparation of 42]
In the preparation of the abrasive slurry 2, abrasive slurries 3 to 42 were prepared in the same manner except that the type of abrasive particles and the addition amount of the surfactant were changed to the combinations shown in Tables 2 and 3. . In addition, regarding pH value, the addition of a pH adjuster was not performed in particular. As a tendency, the pH value shifted to the alkali side with the addition of the surfactant.

[Preparation of abrasive slurry 43-48]
In the preparation of the abrasive slurry 9, abrasive slurries 43 to 48 were prepared in the same manner except that the pH value was changed to the pH values shown in Table 3 using a pH adjuster. In addition, acetic acid or hydrochloric acid was used for pH adjustment to the acid side, and sodium hydroxide was used for adjustment to the alkali side.

<Evaluation of abrasive slurry>
[Measurement of zeta potential of abrasive particles]
Using the electrophoresis Doppler method with "HORIBA nano Partica SZ-100 (Horiba, Ltd.)" which is a nanoparticle analyzer, the zeta potential of each of 500 abrasive particles is measured, and the average zeta is calculated from the arithmetic average value. The potential was measured.

  Specifically, using a medium solution obtained by separating abrasive particles from the abrasive slurry to be measured, 5.0 mass% of the abrasive slurry was diluted 1000 times, and 500 pieces at a liquid temperature of 25 ° C. The zeta potential of the abrasive particles was measured, and the average zeta potential was measured from the arithmetic average value.

[Measurement of pH]
The pH of each abrasive slurry at 25 ° C. was measured using a Lacom Tester desktop pH & conductivity meter (PH1500, manufactured by ASONE Corporation).

[Evaluation of storage stability of abrasive slurry]
Immediately after preparing the abrasive slurry and after stirring and storing at 40 ° C. for 3 days, the primary particle ratio was measured according to the following method to evaluate the storage stability of the abrasive slurry. The primary particle ratio is a scale for measuring the presence or absence of aggregates, and the higher the primary particle ratio, the better the particle uniformity, and the change in the primary particle ratio after stirring and storage at 40 ° C. for 3 days compared to immediately after preparation. The smaller the value, the better the storage stability of the abrasive slurry.

  The primary particle ratio is measured by taking a scanning micrograph (for example, FIG. 8) of the abrasive slurry and presenting the primary particles independently without causing aggregation (secondary particles or more). The abrasive particle ratio was measured.

  Next, the measured primary particle ratio was ranked according to the following criteria.

A: The primary particle ratio is 95% or more. O: The primary particle ratio is 85% or more and less than 95%. Δ: The primary particle ratio is 75% or more and less than 85%. X: The primary particle ratio is 65% or more and less than 75% XX: Primary particle ratio is less than 65% [Evaluation of abrasion scratch resistance]
Using the abrasive slurry immediately after preparation used in the evaluation of the storage stability of the abrasive slurry and the abrasive slurry which was stirred and stored at 40 ° C. for 3 days, the polishing scratch resistance was evaluated according to the following method.

  Each abrasive slurry was circulated and supplied at a flow rate of 5 L / min for polishing. As a polishing object, a 65 mmφ glass substrate was used, and a polishing cloth made of polyurethane was used as the polishing cloth.

The pressure during polishing on the polished surface was 9.8 kPa (100 g / cm ² ), the rotation speed of the polishing tester was set at 100 min ⁻¹ (rpm), and polishing was performed for 30 minutes.

  Next, the range of 50 × 50 mm on the polished glass substrate surface was visually observed to confirm the presence or absence of polishing scratches that could be visually recognized, and the polishing scratch resistance was evaluated according to the following criteria.

◎: No scratches that can be recognized visually are observed. ○: Very weak scratches are generated with no more than one, and there is no problem. △: There are two or less weak scratches, which is practically acceptable. The quality is x: The number of weak scratches is 3 or more and 10 or less, which is a quality that is of practical concern. XX: Many obvious scratches are generated, and this is a quality that is problematic in practice. (Evaluation of polishing rate)
Each abrasive slurry immediately after preparation was circulated and supplied at a flow rate of 5 L / min for polishing. A 65 mmφ glass substrate was used as the object to be polished, and a polishing cloth made of polyurethane was used as the polishing cloth.

The pressure during polishing on the polished surface was 9.8 kPa (100 g / cm ² ), the rotation speed of the polishing tester was set at 100 min ⁻¹ (rpm), and polishing was performed for 30 minutes.

  Next, the thickness (μm) before and after polishing is measured by Nikon Digimicro (MF501), the polishing amount per minute (μm) is calculated from the thickness displacement, and the polishing rate (μm / min) at the start of polishing is calculated. Asked.

  Next, after performing the above polishing process 10 times continuously, the thickness (μm) before and after polishing was similarly measured with Nikon Digimicro (MF501), and the polishing amount (μm) per minute was calculated from the thickness displacement. The polishing rate (μm / min) after polishing 10 times was determined.

  Next, the measured polishing rate was ranked according to the following criteria.

A: The polishing rate is 0.60 μm or more. O: The polishing rate is 0.50 μm or more and less than 0.60 μm. Δ: The polishing rate is 0.40 μm or more and less than 0.50 μm. 30 μm or more and less than 0.40 μm XX: Polishing rate is less than 0.30 μm Table 2 and Table 3 show the results obtained as described above.

  As is apparent from the results shown in Tables 2 and 3, the cores and shells having different compositions defined in the present invention are included, the cores mainly include oxides of yttrium, It has cerium oxide as a component and yttrium oxide as a subcomponent, and the core and shell have at least one oxide of the same metal element (including cerium oxide), and the variation coefficient of particle size distribution is An abrasive slurry containing 20% or less of abrasive particles and having an average zeta potential of the abrasive particles in the range of −120 to −30 mV, the storage stability of the slurry with respect to the comparative example, It can be seen that the polishing flaw resistance and the polishing rate are excellent.

  That is, in the abrasive slurry 1 to 24 containing the abrasive particles having the composition defined in the present invention, the abrasive slurry having an average value of zeta potential in the range of −120 to −30 mV is the storage stability of the slurry, Excellent effect on polishing scratch resistance and polishing rate, but when the data potential exceeds -30 mV, the abrasive particles are aggregated, and the storage stability of the slurry, polishing scratch resistance and polishing rate are deteriorated. I understand. In addition, when the data potential is less than −120 mV, electrical repulsion with a negatively charged glass substrate is particularly high, which causes a reduction in the polishing rate.

  Further, abrasive slurries 25 to 27 including abrasive particles 5 having a uniform composition as a comparative example, and abrasive slurries 28 to 30 each including abrasive particles 6 each having a core composed of yttrium alone and a shell composed of cerium alone. Abrasive particles 9 to 36 having a variation coefficient of particle size distribution exceeding 20% and containing polydisperse abrasive particles 7 and 8, and abrasive particles 9 that do not contain a common element between the core composition and the shell composition In the abrasive slurry 37 to 39 containing, even if the zeta potential of the particles is within the range of −120 to −30 mV defined in the present invention, sufficient slurry storage stability, abrasion scratch resistance and polishing rate are obtained. Can't get.

  Further, by adjusting the pH of the abrasive slurry within the range of 3.0 to 11.0, it was possible to obtain more excellent slurry storage stability, abrasion scratch resistance and polishing rate.

Example 2
<< Preparation of abrasive particles >>
In the preparation of the abrasive particles 2 described in Example 1, the yttrium nitrate used in the formation of the core and shell was samarium (III) nitrate, europium (III) nitrate, gadolinium (III) nitrate, and terbium nitrate (III), respectively. Abrasive particles 13 to 16 were prepared in the same manner except that they were changed to.

  For the prepared abrasive particles 13 to 16, in the same manner as described in Example 1, the measurement of the cerium concentration in the outermost surface region, the measurement of the average particle size, and the measurement of the coefficient of variation of the particle size distribution are performed. Table 4 shows the obtained results.

《Preparation and characteristic evaluation of abrasive slurry》
In the preparation of the abrasive slurries 8, 9, and 11 described in Example 1, the abrasive slurries 49 to 49 were similarly performed except that the above-prepared abrasive particles 13 to 16 were used instead of the abrasive particles 2 respectively. 60 was prepared.

  Next, for each abrasive slurry, the storage stability, abrasion scratch resistance and polishing rate of the slurry were evaluated in the same manner as in the method described in Example 1, and the obtained results are shown in Table 5.

  As is apparent from the results shown in Table 5, almost the same effect can be obtained even when the metal element oxide is composed of samarium oxide, europium oxide, gadolinium oxide, and terbium oxide instead of yttrium oxide. It was.

  Further, abrasive particles formed using titanium (IV) nitrate, strontium nitrate (II), and barium nitrate (II) in the same manner as described above instead of yttrium oxide as the metal element oxide are also shown in Table 5 below. It was confirmed that characteristics similar to those described in (1) can be obtained.

1 Core 2 Shell 3 Yttrium element ratio 4 Cerium element ratio A Abrasive particles

Claims (9)

An abrasive slurry containing core-shell type abrasive particles each having a core and a shell having different compositions,
The core of the core / shell type abrasive particle contains an oxide of at least one metal element selected from the following metal element group as a main component, and the shell contains cerium oxide as a main component and the following metal as a sub component. Containing at least one metal element oxide selected from the element group,
The core and shell contain at least one oxide of the same metal element (including cerium oxide), and the coefficient of variation in the particle size distribution of the core-shell type abrasive particles represented by the following formula (1) 20% or less,
And the average value of the zeta potential of the core-shell type abrasive particles is in the range of -120 to -30 mV.
Metal element group: Ti (titanium), Sr (strontium), Y (yttrium), Ba (barium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium)
Formula (1)
Coefficient of variation of particle size distribution of core / shell type abrasive particles (%) = (standard deviation of particle size distribution of core / shell type abrasive particles / average particle size of core / shell type abrasive particles) × 100   The abrasive slurry according to claim 1, wherein the pH of the abrasive slurry in terms of 25 ° C. is adjusted within a range of 3.0 to 11.0 with a pH adjuster.   The abrasive slurry according to claim 1 or 2, wherein the surfactant is contained within a range of 0.1 to 20% by mass.   The cerium oxide concentration profile in the shell of the core-shell type abrasive particle has a concentration gradient in which the cerium oxide concentration increases from the interface region between the core and the shell toward the outermost surface region of the shell. The abrasive slurry according to any one of claims 1 to 3, wherein:   The average content of cerium oxide in the outermost surface region of the core-shell type abrasive particles is in the range of 60 to 90% by mass, according to any one of claims 1 to 4. The abrasive slurry described.   6. The abrasive slurry according to claim 1, wherein an average value of zeta potential of the core-shell type abrasive particles is in a range of −90 to −40 mV. .   The average particle diameter of the primary particles of the core-shell type abrasive particles is in the range of 0.02 to 2.00 µm. 7. Abrasive slurry.   The core-shell type abrasive particles have a ratio of spherical particles to the total number of core-shell type abrasive particles in the abrasive slurry of 80% by number or more. The abrasive slurry according to any one of the above.   The primary particle ratio (particle%) of the core-shell type abrasive particles is 85% or more within a pH range of 3.0 to 11.0 in terms of 25 ° C. The abrasive slurry according to any one of claims 8 to 9.